The science of attractiveness can be obnoxious when misrepresented, but it's also fascinating. A new book contains some surprising information about sexy tigers, the cosmetic power of veggies — and how to talk about beauty without being an asshole.

David Perrett's In Your Face is all about our perceptions of human facial attractiveness, but it's largely free of the repellent statements that characterize many pop-science treatments of beauty and sexuality. Perrett's not interested in "proving" that fat people are gross or that men simply have to have much younger partners. His book may not be perfect — he uncritically reports research on monkeys' gendered play habits that Cordelia Fine questioned in her also-fascinating Delusions of Gender, and most of the studies he cites focus on heterosexual attraction (a limitation he acknowledges). Nonetheless, In Your Face is packed with interesting stuff. A sampling:

Cordelia Fine's thorough (and funny!) Delusions of Gender punches a giant hole in the idea…
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The person taking the picture matters.
Most studies of human beauty rely on a supposedly objective rating system — and indeed, some studies show surprising cross-cultural agreement on who is hot (while Perrett notes some differences in preferences and body modifications across cultures, he also writes, "if the populations of two countries each ran a beauty competition with the same contestants, all of whom were from a single ethnic background, the votes from the two countries would be likely to be about 90 percent similar"). But a number of factors that have nothing to do with a person's bone structure also influence our perception of his or her hotness. The effects of a woman's menstrual cycle on her preferences are much-vaunted — but to my mind, this tidbit is way more interesting:

Even when they were asked to keep a neutral expression, most women are subsequently judged more attractive in shots taken by a male photographer than in shots taken by a female photographer. Maybe there is a little flirtation from both parties — many men will not be satisfied until they have won a smile from a female. Men are not immune to friendly females, either; even a brief conversation with a woman can make their testosterone soar. In photographs taken after five minutes' chat with a sociable female, men looked significantly happier; they were also voted more attractive as a long-term partner than they were in photos that had been taken after they'd spend five minutes waiting alone.

Eating fruits and vegetables could make you hotter.
In African, Asian, and European study populations, people tend to prefer faces that are yellower in skin tone, an effect caused by eating lots of beta-carotene rich fruits and vegetables. Perrett explains that yellow pigments may be a sign of health, since "when blood supplies are depleted by diseases, fewer carotenoids will be laid down in the skin." Perrett's explanation of the general preference for a healthy-looking mate is nothing you haven't heard before (a partner's illness can harm a fetus or result in faulty genes being passed on), but it's worth noting that not all people put an appearance of health above all else. In fact ...

Anxious people care more about being liked than about healthy skin.
Perrett writes,

Low- and high-anxiety individuals were shown video clips that portrayed people either turning their heads towards the viewer and smiling (as if showing pleasant interest in the viewer) or turning their heads away from the viewer and smiling (as if showing interest directed away from the viewer). The faces in the video clips had been manipulated so that some appeared to be very healthy and some appeared to be unhealthy. Low-anxiety individuals liked the healthy faces who showed social interest in them, but not the unhealthy ones. High-anxiety individuals, on the other hand, liked anyone smiling at them, whether healthy or unhealthy.

As Perrett points out, this shows that even though some studies show general consensus on some aspects of beauty, this one proves that "no single set of facial characteristics makes us attractive — or unattractive — to everyone." This may seem somewhat contradictory, but then again, it's not odd that in situations closer to real-world interaction — a face that's actually moving and not static — a diversity of opinions begins to emerge. Even if people deem the same kinds of faces beautiful in a context-free photo, that doesn't mean all people want to fuck, date, or marry an identical partner.

You can (sort of) judge a book by its cover.
Says Perrett,

From the face alone, others can make a good guess at whether we prefer sexual relations only in the context of long-term loving relationships or whether we are open to short-term sexual encounters without the necessity of love. [...] Photographs of people who had already self-rated themselves as a devoted lover or a no-strings person were shown to strangers who were asked to identify which sexual practice each person was likely to follow. Generally speaking, people could identify the two types of men and women [...] although women were better at doing this than men.

People can also supposedly detect extroversion and introversion in people's faces. I, however, totally sucked at this, possibly because I'm more introverted (extroverts are better at spotting extroversion) and possibly because I'm just such a sweetheart — says Perrett, "warm-hearted and generous people are very poor judges of personality in faces." Here, see if you're as kind and easily fooled as I am:

Some tigers are hotter than others.
Perrett claims that most people can spot the more attractive of these two tigers. I could not, probably because I'm too darn warm-hearted. I am probably destined to be deceived by a crafty tiger who pretends to be a devoted lover when really he just wants to eat me.

Some of the findings in In Your Face may be controversial — especially those having to do with cross-cultural beauty preferences — but it's possible to talk about them in a way that's not reductive. First, we need to acknowledge (as Perrett does) that what humans like in photos may not always be the same thing they like in partners, whether for life or for the night. And second, we shouldn't allow the science of attractiveness to dictate morality or politics — just because subjects in one study like a certain type of face doesn't make that face better and all others worthy of shaming, nor does it mean that anyone whose partner's face doesn't "measure up" is justified in cheating. As long as we're aware of the limits of science and don't try to use it as an excuse for bad behavior, we can learn some fascinating stuff — and maybe challenge some preconceived notions while we're at it.